Practice question

Dominant trait requires at least one copy of mutant allele in genotype to manifest phenotype. Unaffected individuals lack mutant allele completely, genotype homozygous recessive normal, so they possess no dominant allele to transmit to offspring. Therefore two unaffected parents produce only unaffected offspring for fully penetrant autosomal dominant disorder, barring new mutation. Transmission requires at least one affected parent carrying allele. This contrasts sharply with recessive inheritance where unaffected heterozygote carriers can transmit allele silently to children, explaining differences in pedigree patterns observed clinically.